Fatty acid and retinol-binding protein: A novel antigen for immunodiagnosis of human strongyloidiasis

PLoS One. 2019 Jul 22;14(7):e0218895. doi: 10.1371/journal.pone.0218895. eCollection 2019.

Abstract

The tenacious human parasitic helminth Strongyloides stercoralis is a significant health problem worldwide. The current lack of a definitive diagnostic laboratory test to rule out this infection necessitates designing more specific diagnostic methods. Fatty acid and retinol-binding protein (FAR) plays a crucial role in the development and reproduction of nematodes. We generated a recombinant form of this protein and determined its applicability for immunodiagnosis of S. stercoralis. The L3 form of S. stercoralis was harvested and used for RNA extraction and cDNA synthesis. The coding sequence of S. stercoralis FAR (SsFAR) was cloned into pET28a(+) vector, expressed in E. coli BL21 and purified. ELISA and immunoblotting were employed to determine the specificity and sensitivity of rSsFAR using a set of defined sera. In addition, we analyzed the phylogenetic relationship of SsFAR with different FAR sequences from other nematodes. The cloned SsFAR had an open reading frame of 447 bp encoding 147 amino acids, with a deduced molecular mass of 19 kD. The SsFAR amino acid sequence was 93% identical to FAR of S. ratti. For differential immunodiagnosis of strongyloidiasis, rSsFAR exhibited 100% sensitivity and 97% specificity. However, cross-reactivity with FAR proteins of other parasites, namely Toxocara canis and Echinococcus granulosus, was noted. Our results provide a novel approach for immunodiagnosis of S. stercoralis infections using rSsFAR with reliable sensitivity and specificity.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antibodies, Helminth / immunology
  • Antigens, Helminth / immunology
  • Antigens, Helminth / isolation & purification
  • Diagnostic Tests, Routine
  • Enzyme-Linked Immunosorbent Assay
  • Escherichia coli / genetics
  • Fatty Acids / genetics
  • Fatty Acids / metabolism
  • Humans
  • Immunologic Tests / methods
  • Phylogeny
  • Recombinant Proteins / genetics*
  • Recombinant Proteins / immunology
  • Recombinant Proteins / isolation & purification
  • Retinol-Binding Proteins / genetics*
  • Retinol-Binding Proteins / isolation & purification
  • Strongyloides stercoralis / genetics*
  • Strongyloides stercoralis / immunology
  • Strongyloides stercoralis / pathogenicity
  • Strongyloidiasis / diagnosis*
  • Strongyloidiasis / genetics
  • Strongyloidiasis / immunology
  • Strongyloidiasis / parasitology

Substances

  • Antibodies, Helminth
  • Antigens, Helminth
  • Fatty Acids
  • Recombinant Proteins
  • Retinol-Binding Proteins

Grants and funding

This research was supported by grant number 27828 from Iran University of Medical Sciences, Tehran, Iran, which was delivered to AR Meamar. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.